The invention relates to a control system and circuit for use with a vehicle having one or more axles. More particularly, the invention relates to a hydrostatic drive circuit where a controller and hydrostatic motors and pumps are used for propelling and controlling the torque of wheels or drive tracks in a vehicle such as an agricultural vehicle, row crop sprayer, or off-road vehicle.
U.S. Pat. No. 5,931,078 entitled Hydrostatic Drive System, relates to a hydrostatic drive system with a demand-responsive pump and at least one hydraulic circuit or consumer connected to it. U.S. Pat. No. 5,890,982 entitled Continuous Hydrostatic-Mechanical Branch Power Split Transmission Particularly For Power Vehicles, relates to a hydrostatic/mechanical branch power split transmission for power vehicles. U.S. Pat. No. 5,823,072 entitled Vehicle Drive System, discloses a vehicle drive system for mobile hydraulics having a hydrostatic power transmission and a multi-speed selector gear. U.S. Pat. No. 5,782,091 entitled Hydrostatic Continuously Variable Transmission, concerns a continuously variable hydrostatic transmission including a constant displacement type swash plate hydraulic pump and a variable displacement type swash plate hydraulic motor. U.S. Pat. No. 5,683,322 entitled Continuous Hydrostatic-Mechanical Branch Power Split Transmission Particularly For Power Vehicles, relates to a hydrostatic/mechanical branch power split transmission for power vehicles. U.S. Pat. No. 5,628,188 entitled Torque Control Of Hydrostatic Machines Via The Pivot Angle Or The Eccentricity Of Said Machines, discloses a circuit arrangement for controlling the output torque of a hydrostatic machine connected to a hydraulic system having an impressed operating pressure. U.S. Pat. No. 5,615,748 entitled Earth-Based Vehicle concerns a vehicle including a main frame structure, a track assembly mounted to the main frame structure and having an single, endless ground-engaging track extending in a longitudinal direction. A pair of steerable ground-engaging wheels flank the track, and are constructed and arranged to exert a ground bearing pressure sufficient to change a direction of travel of the track in response to turning of the wheels to steer the vehicle.
The above and other documents cited herein are incorporated herein by reference in their entireties and for all purposes. They disclose systems having utility, but leaving an unmet need for a system that tends to optimally distribute torque among vehicle wheels under a variety of operating conditions.